A radial direction controller is per se known that is applied to a magnetic bearing apparatus that supports a rotating body by the operation of opposing electromagnets so that the rotating body levitates. And such a radial direction controller is per se known that is provided with a negative bearing stiffness elimination circuit for eliminating negative bearing stiffness, which is negative position stiffness with increasing of the attractive force according to the amount that an electromagnet and the rotating body approach one another (for example, refer to Patent Document #1).
Patent Literature—Patent Document #1: Japanese Laid-Open Patent Publication No. 2009 63005.